Radio communication devices include a transmitter and/or receiver coupled to an antenna which emits and/or detects radio frequency signals. The device may include a microphone for inputting audio signals to a transmitter or a speaker for outputting signals received by a receiver. Examples of such radio communication devices include one way radios, two way radios, radio telephones, personal communication devices, and a variety of other equipment. These communication devices typically have a standby configuration, wherein the device is collapsed for storage, and an active communication configuration, wherein the antenna is extended for optimum performance.
For radio telephones and two-way radios, it is typically desirable that these devices have a small size during a standby mode to facilitate storage and transport thereof. For example, users prefer that the radio telephones are small enough in the standby mode to permit storage in a shirt or jacket pocket. In the active communication state, it is desirable for the device to be sufficiently long to position the speaker adjacent to the user's ear, the microphone near the user's mouth, and the antenna away from the user's body. It is desirable for the antenna to be positioned away from the user's body since the user's body is a large conducting object that interferes with radio frequency signal reception. One particularly effective way of positioning the antenna away from the user's body is to extend the antenna away from the device body during use. By providing an antenna which collapses for storage and extends for active communication, an antenna with optimum active mode operation is provided in a readily storable device.
A difficulty encountered with such reconfigurable communication devices is providing a high performance antenna in the standby mode. For example, radio telephones are known that receive paging signals, electronic mail, and call alerting signals in the standby mode. However, the body of the device, including the internal electronic circuitry within the body, is typically in the reactive near-field of the antenna in the storage position. These conductive objects in the reactive near-field degrades performance of the antenna, which is detrimental to signal reception in the standby mode.
An example of a radio communication device including a multi-position antenna is a radio telephone including a body and, wherein the flap incudes an antenna mounted thereon. When closed, the flap covers the radio telephone key pad and provides a compact housing. When the flap is opened, the flap antenna is spaced from the telephone body which the user holds. Although the flap antenna performs very well when the flap is open, the proximity of the radio telephone body in the closed flap position interferes with the operation of the antenna in the collapsed standby mode.
Accordingly, it is desirable to provide an antenna system having high performance characteristics when the communication device is extended in an active communication mode and when the communication device is collapsed in a standby mode of operation.